Carrier-current relay system



Patented Aug, i940 UNITED STATES CARRIER-CURRENT RELAY SYSTEM Bernard E. Lenehan, Bloomfield, N. J., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh Pennsylvania Paf., a' corporation of ApplicatiolrMay 5, 1939, Serial No. 271,953

16 Claims.

My invention relates to carrier-current protective relaying-systems for the detection of faults in polyphase transmission-lines, and it has particular reference to so-called intermittent carrier systems with receiver-relays normally biased to non-tripping position, that is, to carrier-current systems of the type in-which the carrier-curr'ent transmitter is normally in a non-transmitting condition, and in which the carrier-current receiver-relay is normally in a non-tripping condition. I'he principal novel feature of my invention is the utilization of a single dual-purpose directionally sensitized fault-responsive relay which is utilized both for initiating carrier-current transmission and for' energizing a tripping circuit in conjunction with the receiver-relay.

In intermittent carrier systems With normally biased receiver-relays, it has been found necessary, for various reasons, to utilize two separate fault-responsive relays for initiating the carriercurrent transmission andA controlling the tripping circuit in conjunction with the carrier-current receiver, respectively. 'I'his has been done in order to make sure that the carrier-initiating relay would always respond either prior to, or at least substantially as soon as, the trip-circuit, faultdetector relay which is associated with the car- Iier-current receiver-relay. It is necessary for the carrier current to be superimposed on the line, or' on the pilot-channel between the two ends of the protected line-section, at least as soon as the above-mentioned trip-circuit faultdetector relay is energized, because said tripcircuit fault detector relay is also utilized to cause the receiver-relay to tend to close its tripcircuit contacts, and the carrier-current energy is utilized to hold or lock the receiver-relay in its normal non-tripping position, which must be done until the line-current directional relays can come into play and properly control the continuance or discontinuance of the carrier-current transmission in accordance with the line-current direction at the respective relaying points.

Ever' since soon after the intermittent carrier system with normally biased receiver-relays was vfirst tried out, itshas been the standard practice (Cl. F75-294) rately that the relay which is remotest from the fault will not occasionally pick up an appreciable time sooner than the corresponding relay at the other end of the protected line-section, particularly in the case of fault-detector relays other than those of the distance-responsive type, and also in the case of distance-relays of a far distance-setting. Under such circumstances, if the same fault-detector were utilized for carrierinitiation and tripping, the carrier current may be put on the line by the fault-detector which responds first, and it may be taken ofi of the line by the directional relay-element at the same station, responding to currents flowing into the protected line-section at said station, all before carrier current is even initiated at the other end of the protected line-section, thus resulting in a faulty tripping operation thr'ough the receiverrelay contacts at the first-mentioned end.

Another reason for requiring two relays of different sensitivities, in the past, is that, during out-of-synchronism conditions, when the linecurrents are increasing and decreasing in magnitude relatively slowly, so that the fault-detector .relays are not suddenly impressed with currents of a value amply suicient to actuate the r'elays, as in the normal case of fault-currents, but the fault-detector relays are slowly impressed with only gradually changing currents, the relays must operate on their threshold-values, where their time of operation is necessarily slow, and where it is impossible to coordinate the times of response of two distantly located relays at opposite ends of a protected line-section, except by having one relay definitely more sensitive than the other.

The object of my present invention is to produce a simplified carrier-current relaying-system of the type just discussed, in which I obviate the necessity for utilizing two separate relays, of different sensitivitiesl for initiating carrier and controlling the tripping-circuit through the receiver-relay, respectively. I accomplish this purpose by the simple expedient of causing my double-duty, fault-detector relaying-means to be relatively strongly responsive to a line-current function, an-d relatively weakly responsive to an electrical line-quantity which exists concurrently with said line-current function and which is of a uniform polarity regardless of the direction of the line-current, so that the fault-detector relaying-means is actuated in response to the vectorial sum of the two responses, the two responses being cumulative when the line-current is flowing out of the protected line-section, so that the relay is more sensitive for this direction of line,

current flow than when the line-current is owing into the protected line-section. Throughout the specification and in the appended claims, I refer to the line-current flowing into the protected section as being indicative of the presence of a fault on the protected-section side of the station-bus at the point where the relay is located. The uniform-polarity line-quantity may either be a line.. voltage component or a current which is fed into the line at the relaying point regardless of whether the fault is on one side or the other side of the station-bus.

The principal object of my invention is to utilize a dual-purpose directionally sensitized fault-responsive relay of the above-described nature for the purpose of both initiating the carrier-current transmission and assisting in the control of the tripping-response of the receiverrelay and in the completion of the trippingcircuit of the line-sectionalizing circuit-interrupters at the relaying point.

A still more specific object of my invention is the particular application of the abovementioned principles to ground-relays which have heretofore involved particularly difficult problems in connection with the protection vof polyphase transmission systems.

With the foregoing andgother objects in view, my invention consists in the apparatus, combinations, circuits, systems and methods hereinafter described and claimed, and illustrated in the accompanying drawing, wherein:

Figure 1 is a simplified diagrammatic view of circuits and apparatus embodying my invention in connection with a ground-detector relay utilizing a transformer neutral current of a powertransformer bank as the directionally sensitizing and desensitizing means dependent upon the direction of the line-current.

Fig. 2 is a diagrammatic view of a portion of the circuit shown in Fig. 1, illustrating a modification in the alternating-current control-circuits for the directionally sensitized ground-fault relay, in which the directionally sensitizing and desensitizing force is obtained from the zero-phasesequence voltage-component supplied by the open-delta secondary-circuit of a bank of potential transformers, the directionally sensitized relay itself being modied by having two operating coils as distinguished from a doubly-fed single coil, as in Fig. 1,

Fig. 3 is an across the line diagram of the direct-current connections of the systems shown in Figs. 1 and 2, and

Fig. 4 is a view, similar to Fig. 2, illustrating the application of my invention to a phase-fault relay rather than a ground-fault relay.

In Fig. 1 I illustrate the relaying equipment for one end of a protected line-section LI of a three-phase transmission-line, such illustration being representative of the equipment at all of the other line-section terminals. The protected line-section LI, comprising the three phaseconductors a, b and c, is joined, by means of an oil circuit-breaker 3, to a station-bus 4 which is illustrated as having another line section L2 connected thereto, and as being energized also from a generator G which is connected to the bus through a bank of power-transformers 5, the bus-terminals of which are Y-connected so as to provide a grounded neutral circuit 6. The line circuit-breaker 3 is provided with a tripcoil 1, and with an auxiliary contact 8 which is closed whenever the circuit breaker is closed, and opened whenever the circuit breaker opens its main contacts. The trip-coil l is adapted to be energized, in series with the auxiliary switch 8, from a tripping battery 9, the terminals of which are indicated at and The relaying system shown in Fig. 1 is a carrier-current system utilizing a carrier-current transmitter Il and a carrier-current receiver I2 which are coupled to an inductance device i3 which is connected, through a coupling capacitor I4, between the phase-C line-conductor and ground, the carrier currents being more or less confined to said phase-C conductor by means of a wave-trip'l.

The carrier-current transmitter Il is diagrammatically illustrated as comprising an oscillatortube I6 which has a cathode I1, a grid i8 and an anode I9, and it is energized by means of a B-battery, the terminals of which are indicated at B+ and B-. The carrier-current receiver l2 is diagrammatically represented as comprising a tube 2| having a cathode 22, a grid 23 and an anode 24, the receiver being also energized from the B-battery which is represented by the terminals B- and B+.

The relaying equipment comprises a carriercurrent receiver-relay RR having a normally open relay-contact 26, a holding-coil RRH for strongly holding the receiver-relay in its normal open-contact position, and a so-called tripping or actuating coil RRT for causing the receiver-relay to respond so as to move to its closed-contact position in the absence of the restraint which is imposed by the holding-coil RRH when the latter is energized. The receiver-relay is also provided with a polarizing means in the form of a permanent magnet as indicated by the letters N and S.

In Fig. 1 I have shown only the ground-fault protective apparatus, it being understood, of course, that phase-fault protective apparatus may also be utilized, if desired, as would usually be the case. The ground-fault relays consist of a ground-overcurrent fault-detector relay IO and a ground-directional relay DO, the grounddetector relay IO being provided with two makecontacts 21 and 28, respectively, and the grounddirectional relay DO being provided with a makecontact 29.

The ground-directional element DO is provided With directional terminals 3l, and polarizing terminals 32, so that the relay compares the relative directions of the currents in the two terminals. The directional terminals 3| are energized responsively to the zero-phase sequence or ground-current component of the linecurrents, by being connected in the residual circuit of a bank of star-connected line-current transformers 33, which are also utilized to energize any desired phase-current-responsive apparatus which is symbolized at A, B and C. The polarizing terminals 32 of the ground-directional relay DO are energized responsively to the current flowing in the grounded neutral circuit 6 of the bank of power transformers, by means of an auxiliary current-transformers 34.

In accordance with my invention, in the particular form of embodiment illustrated in Fig. 1, the operating coil of the ground-detector relay IO is relatively strongly energized from the residual-current circuit of the line-current transformers 33, and relatively weakly energized from the auxiliary current-transformer 34 which responds to the transformer-neutral current, these two exciting currents, for the ground-detector IO, being combined by connecting the currenttransformer sources of relaying-current energy in parallel with each other.-

In Fig. 1, I have illustrated two different faultlocations for possible ground-faults on one phase, such as phase-C, of the transmission system. One ground-fault location is indicated at X, on the same side of the station-bus 4 as the line-section L2, while the other suggested ground-fault location is indicated at Y, on the other side of the station-bus 4, or on the same side as the protected line-section LI. In general, the groundfault locations which are the most critical, from a relaying standpoint, will be removed quite far away from the station-bus 4, further away than the length of the protected line-section, the idea of distance being conveyed by dotted lines.

The ground-fault currents which flow through the line-current transformers 33 are indicated by the arrows Ixo and Iyo, respectively. For simplicity of discussion. I will assume that substantially all of the outwardly flowing ground-fault current Ivo flows upwardly in the transformerneutral connection 6, when the ground-fault location is far to the right, as indicated at Y, and that a substantial increment I'xo of ground-fault current also flows upwardly in the illustrated 'transformer-neutral circuit 6, so as to join with the current-component Ixo of the line-current transformers 33, to provide the total groundcurrent (Ixo-l-Ixo) which flows to the groundfault when the location of the latter is far to the left, as indicated at X. In each case, whether the ground-fault is at X or at Y, it is assumed that the ground-fault current is flowing from the line into the ground at the faulted point. It will be observed, therefore, that the transformer neutral current, which is reflected in the auxiliary current-transformer 34, is always in the same direction of polarity regardless of whether the line-current zero-sequence component flows to the left, as at Ixo, or to the right as at Ivo.

In Fig. 1, I have illustrated the relatively strong response of the line-current transformers 33 by the factor K, and the relatively weak response of the auxiliary current-transformer 34 by the factor or ratio 7c, it being understood that K is considerably larger than lc. By way of example, but not by way of limitation, it may be assumed that k is about 5% of K. The drawing indicates, in Fig. 1, the relaying currents supplied by the respective transformers 33 and 34 for each of the fault-locations X and Y, and also the composite or resultant relay-currents (KIxo-l-kl'xo) or (KIYo-cIYo) which are supplied to the operating coil of the ground-detector relay IO.

It thus appears that the ground detectorrelay IO is more strongly energized when the ground-current component is flowing through the line-current transformers 33 in a direction out of the protected line-section LI and toward the bus 4, as indicated at Ixo, than when the groundcurrent component is flowing through the linecurrent components 33 in a direction away from the bus 4 and into the protected line-section LI, as indicated at Ixo. If, therefore, the fault is outside of the protected line-section LI, so that the same current appears in the line-current transformers 33 at both ends of the protected line-section, whether the current is flowing to the right, as Ixo, or to the left, as Ixo, the grounddetector IO at the end where the current is `leaving the protected line-section LI will be more strongly energized, and hence more sensitive, than the other ground-detector IO at the end where the current is entering the protected linesection, thus ensuring that the ground-detector at the entering-current end shall not operate before the ground-detector at the leaving-current end.

I wish it to be understood, in the interpretation of my illustrated embodiment in Fig. 1, that the dual-purpose ground-detector relayingmeans IO is susceptible of several forms of physical embodiment, and that the means for weakly polarizing it, so that it will be more sensitive to outwardly owing currents than inwardly flowing currents, is also to be regarded as symbolic of any means for responding to a properly uniformly directed electrical line-quantity.

Thus, in Fig. 2, the station-bus 4 is illustrated as being connected to the two line-sections LI and L2, and also to a third line 40 which is connected thereto through a power-transformer bank 4|, the bus-side of which is star-connected and grounded, as indicated at 42. In Fig. 2, the ground-detector relay IO, instead of having a single, doubly excited operating-coil, is provided with a main operating coil 43 and an auxiliary operating coil 44, the latter having a much smaller number of turns, both`operating coils being wound so as to magnetize the same magnetizable circuit 45 for producing the actuating force for operating the ground-detector relay IO. The main operating winding 43 is energized solely from the residual circuit of the line-current transformers 33, while the auxiliary operating winding 44, in Fig. 2, is illustrated as being energized from the open-delta secondary-windings 46 of a bank of star-connected potential-transformers 46 which are energized from the station-bus 4.

Thus the open-delta potential-windings 46 in Fig. 2 produce a voltage which is proportional to the zero-phase-sequence component of the linevoltage, but the zero-phase-sequence component of the line-voltage is, in turn, proportional to the impedance-drop resulting from the ow of the zero-phase-sequence component of the line-current from the point of the fault to the relaying 'point or station-bus 4, so that the current in the open-delta potential windings 46 is also proportional or responsive, in a way, to the groundfault currents Ixo and IYo, as indicated by the arrow lcIxo or kIYo.

Referring back again, to Fig. 1, where the entire circuit for one end of the protected linesection LI is indicated. it will be noted that I also provide, in the illustrated embodiment of my invention, an auxiliary relay or contacter-switch which is marked CSG, and which has two makecontacts 41 and 48.

The direct-current circuits are illustrated in both Fig. 1 and Fig. 3, and they comprise the following connections. The trip-circuit, for effecting a line-sectionalizing operation of the circuit-breaker 3, may be traced from the positive battery-terminal (-1-) through the make-contact 29 of the directional element DO, the make- Contact 21 of the fault-detector element IO, the make-contact 26 of the receiver-relay RR, the trip-coil 1, and the auxiliary circuit-breaker contact 8, to the negative battery-terminal The operating coil of the auxiliary relay CSG is energized in a circuit which may be traced from the positive terminal through the makecontact 29 of the directional-element DO, the make-contact 21 of the fault-detector IO, the operating coil CSG and the negative terminal The grid I8 of the oscillator-tube I8 is adapted to be connected to the positive terminal of the tripping battery 9 through a resistor RI and the make-contact 28 of the fault-detector IO; and the grid I8 is connected to the negative terminal of the tripping battery 9 through the resistors RI and R2. The cathode I1 of the oscillator-tube I6 is connected to the positive terminal of the tripping battery which thus serves as a C-battery, or grid-biasing battery, for the transmitter. 'I'he CSG relay-contact 41 is utilized to short-circuit the resistor R2 between the grid I8 and the negative terminal of the tripping battery.` The CSG relay-contact 48 is utilized to energize the tripping coil RRT of the receiver-relay. The holding coil RRH of the receiver-relay is energized inthe plate-circuit of the receiver-tube 2|, which may be traced from the B-battery terminal B+, through the coil RRH, the anode 24, and the cathode 22, to the B-battery terminal B-.

In normal operation, when there is no fault on the transmission line, the oscillator grid I8 is disconnected from the oscillator cathode I1 by the open IO relay-contact 28, so that the transmitter Y II is not oscillating or transmitting carrier-current into the pilot-channel provided by the carrier-current coupling I3-I4.

As soon as a ground-fault occurs anywhere on the transmission system within the reach of the IO relay, the IO relay-contact 28. will close, initiating carrier-current transmission. As previously noted, if the fault is not within the protected line-section LI, the fault-current will be entering the protected section at one end and leaving it-at the other end, with the same faultcurrent ilowing at both ends, but the fault-detector IO at the end Where the current is leaving the protecteed section will be the more sensitive, because of the elect of my directionally sensitizing means, and hence this particular faultdetector relay will be certain to respond at least as soon as the corresponding relay at the other end of the protected line-section.` As soon as carrier-current transmission is established, the

receivers I2 at both ends of the protected linel section immediately energize the respective holding coils RRH of the associated receiver-relays RR, thus making it impossible for the respective receiver-relay tripping coils RRT to cause a response of the respective receiver-relays.

At the end or ends of the protected linesection at which the fault-current is entering the section, assuming any fault within the reach of the fault-detector relay IO, both the directional relaying-means DO and the fault-responsive relay-means IO will respond, closing their contacts 29 and 21, respectively, and energizing the CSG relay at that relaying station or stations. 'I'he response of the CSG relay results in the instantaneous discontinuance of carriercurrent transmission at that station, by the closure of the relay-contact 41, and at the same time it results also, through the relay-contact 48, in the energization of the receiver-relay tripping coil RRT at that station. The energization of the receiver-relay tripping coil RRT produces -no response of the receiverrelay RR unless the carrier-current transmission is discontinued at both ends ofthe protected section, as a result of the response of the directional element DO at each end, in which case the receivers I2 at the respective ends Will cease to energize their respective holding coils RRH, permitting the tripping coils RRT to bring about a response of their respective receiverrelays RR, thus closing the receiver-relay contacts 26 and completing the tripping circuit at both ends of the protected line-section.

It Will be apparent that the basic principles of my invention'are not limited, in their application, to ground-fault protective relaying-systems.

Thus, Fig. 4 illustrates, by way of example, the application of the basic principles of my invention to a phase-fault elay, only phase-C being shown, for simplicity of illustration, although it should be understood that the embodiment in Fig. 4 is' illustrative of any phase-fault relay or relays, either in the form of a'polyphase relay, three phase-to-ground relays, or three line-toline relays. v

In Fig. 4, the station-bus 4 is illustrated as being connected to the two line-sections LI and L2, and as being energized by a generator G which supplies fault-current IC or Iyc to a fault, according to its location at X or Y, as previously explained, this generator-current being of the same polarity, or in the same direction, regardless of Whether the fault lies to the right or the left of the station-bus ,4. A strong response of the phase-fault relay IC is attained from the lnecurrent by means of the line-current transformer 53, and a weak response of the phase-fault relay IC to the generator-current is attained by means of the auxiliary current-transformer 54, in a manner previously explained in connection with Fig. 1. The phase-fault relay IC in Fig. 4 is represented as having two make-contacts 51 and 58 which are utilized, respectively, for tripping and for carrier-current initiation, as will be readily understood from the previous explanations.

While I have illustrated my invention in certain illustrative forms, designed to illustrate the principles thereof, I wish it to be understood that such illustration, and the corresponding description, is intended only by way of illustration and not by way of limitation. I Wish it to be distinctly understood, for example, that my invention is applicable to any fault-responsive relay, Whether of the overcurrent type, or of a type having a restraining electro-magnetic force as well as an operating electromagnetic force, as is in the well-known impedance or distanceresponsive relays. While, for simplicity of illustration, I have illustrated only the means of obtaining the actuating or operating magnetic forces in the relay, in the various illustrated forms of my relay, I Wish it to be distinctly uhderstood that such illustration does not imply that the relay may not also have means for producing a restraining electromagnetic force, or any other means in addition to the illustrated means. I desire it to be understood that the foregoing and other changes, which will be obvious to those skilled in the art, may be made without departing from my invention, and that the appended claims are to be accorded the broadest interpretation consistent with their language and the prior art.

I claim as my invention:

l. Protective relaying equipment for a transmission-line, including a signal-current pilotchannel between the ends of a line-section to be protected, and further including, at each of said ends, a normally non-transmitting signal-current transmitter and a signal-current receiverrelay associated with said pilot-channel, a linesectionalizing circuit-interrupter means, a

double-duty fault-detector relaying-means comprising an actuating member having a magnetizable circuit and magnetizing means for said magnetizable circuit, means for energizing said magnetizing means so as to be relatively strongly responsiveto a line-current function and relatively weakly responsive to an electrical linequantity which exists concurrently with said line-current function and which is of a. uniform polarity regardless of the direction of the linecurrent, the two responses being cumulative when the line-current is iiowing out of the protected line-section, a directional relaying-means responsive to line-fault conditions, means for utilizing a response of said double-duty faultdetector relaying means for causing the transmitter to transmit signal-current into said pilotchannel, means responsive to a receipt of signalcurrent for restraining said receiver-relay against responding, means responsive jointly to a response of said double-duty fault-detector relaying-means and to a predetermined condition of said directional relaying-means for causing a response of said receiver-relay in the absence of said restraint and for preventing said transmitter from transmitting signal-current into said pilot-channel, and means triply responsive to a response of said double-duty faultresponsive relaying-means, a predetermined condition of said directional relaying-means, and a response of said receiver-relay, for effecting a line-sectionalizing operation of said circuit-interrupter means.

2. Protective relaying equipment for a transmission-line, including a signal-current pilotchannel between the ends of a line-section to be protected, and further including, at each of said ends, a normally non-transmitting signal-current transmitter and a signal-current receiverrelay associated with said pilot-channel, a linesectionalizing circuit-interrupter means, a double-duty fault-detector relaying-means comprising an actuating member having a magnetizable circuit and magnetizing means for said magnetizable circuit, means for energizing said magnetizing means so as to be relatively strongly responsive to a line-current function and relatively weakly responsive to an electrical linequantity which exists concurrently with said line-current function and which is of a uniform polarity regardless of the direction of the linecurrent, the two responses being cumulative when the line-current is flowing out of the protected line-section, means for utilizing a response of said double-duty fault-detector relayingmeans for causing the transmitter to transmit signal-current-into said pilot-channel, means for utilizing a response of said double-duty faultdetector relaying-means in the control of said circuit-interrupter means and in the control of said receiver-relay, line condition-responsive directional means, means for utilizing said directional means in the blocking of signal-current transmission, means for utilizing the receipt of signal-current in the control of said receiverrelay, and means for utilizing a response of said receiver-relay in the aforesaid control of said circuit-interrupter means.

3. Ground-fault-protective relaying equipment for a polyphase transmission-line, including a signal-current pilot-channel between the ends of a line-section to be protected, and further including, at each of said ends, a normally non-transmitting signal-current transmitter and a signalcurrent receiver-relay associated with said pilotchannel, a line-sectionalizing circuit-interrupter means, a double-duty fault-detector relayingmeans comprising an actuating member having a magnetizable circuit and magnetizing means for said magnetizable circuit, means for energizing said magnetizing means so as to -be relatively strongly responsive to zero-phase-sequence line-current components and relatively weakly responsive to a zero-phase-sequence line-quantity which exists concurrently with said zero-phase sequence line-current components and which is of a uniform polarity regardless of the direction of the Zero-phase-sequence line-current component, the two responses being cumulai ive when the zero-phase-sequence line-current component is flowing out of the protected line-section, a directional relaying-means responsive to fault conditions, means for utilizing a response of said double-duty fault-detector relaying-means for causing the transmitter to transmit signal-current into said pilot-channel, means responsible to a receipt of signal-current for restraining said receiver-relay against responding, means responsive jointly to a response of said double-duty faultdetector relaying means and to a predetermined condition of said directional relaying-means for causing a response of said receiver-relay in the absence of said restraint and for preventing said transmitter from transmitting signal-current into said pilot-channel, and means triply responsive to a response of said double-duty fault-responsive relaying-means, a predetermined condition of said directional relaying means, and a response of said receiver-relay, for effecting a line-sectionalizing operation of said circuit-interrupter means.

4. Ground-fault-protectlve relaying equipment for a polyphase transmission-line, including a signal-current pilot-channel between the ends of a line-section to be protected, and further including, at each of said ends, a normally nontransmitting signal-current transmitter and a signal-current receiver-relay associated with said pilot-channel, a line-sectionalizing circuit-interrupter means, a double-duty fault-detector relaying-means comprising an actuating member having a magnetizable circuit and magnetizing means for said magnetizable circuit, means for energizing said magnetizing means so as to be relatively strongly responsive to zero-phase-sequence linecurrent components and relatively weakly responsive to a zero-phase-sequence line-quantity which exists concurrently with said zero-phase sequence line-current components and which is of'a uniform polarity regardless of the direction of the zero-phase-sequence line-current component, the two responses being cumulative when the zerophase-sequence line-current component is owing out of the protected line-section, means for utilizing a response of said double-duty faultdetector relaying-means for causing the transmitter to transmit signal-current into said pilotchannel, means for utilizing a response of said double-duty-fault-detector relaying-means in the control of said circuit-interrupter means and in the control of said receiver-relay, line-conditionresponsive directional means, means for utilizing said directional means in the blocking of signalcurrent;` transmission, means for utilizing the receipt of signal-current in the control of said receiver-relay, and means for utilizing a response of said receiver-relay in the aforesaid control of said circuit-interrupter means.

5, Ground-ault-protective relaying equipment for a polyphase transmission-line, including a signal-current pilot-channel between the ends of a line-section to be protected, and further including, at each of said ends, a normally nontransmitting signal-current transmitter and a signal-current receiver relay associated with said double-,duty fault-detector relaying-means for causing the transmitter to transmit signal-current into said pilot-channel, means responsive to :a receipt of signal-current for restraining said receiver-relay against responding, means responsive jointly to a response of said double-duty faultdetector relaying-means and to a predetermined condition of said directional relaying-means for causing a response of said receiver-relay in the absence of said restraint and for preventing said transmitter from transmitting signal-current into said pilot-channel, and means triply responsive to a response of said double-duty fault-responsive relaying-means, a predetermined condition of said directional relaying-means, and a response of said receiver-relay, for effecting a line-sectionalizing operation of said circuit-interrupter means.

6. Ground-fault-protective relaying equipment fora polyphase transmission-line, including a signal-current pilot-channel between the ends of a line-section to be protected, and further including, at each of said ends, a normally non-transmitting signal-current transmitter and a signalcurrent receiver-relay associated with said pilotchannel, a line-sectionalizing circuit-interrupter v means, means for providing a grounded-neutral connection to said transmission-line, a doubleduty fault-detector relaying-means comprising an actuating member having a magnetizable circuit and magnetizing means for said magnetizable circuit, means for energizing said magnetizing means so as to be relatively strongly responsive to. zero-phase-sequence line-current components and relatively weakly responsive to zerophase-sequence line-voltage components, the two responses being cumulative when the zero-phasesequence line-current component is owing out` of the protected line-section, means for utilizing a response of said double-duty fault-detector relaying-means for causing the transmitter to transmit signal-current into said pilot channel, means for utilizing a response of said double-duty fault-detector relaying-means in the control of said circuit-interrupter means and. in the control of said receiver-relay, line-condition-responsive directional means, means for utilizing said directional means in the blocking of signal-current transmission, means for utilizing the receipt of signal-current in the control of said receiverrelay, and means for utilizing a response of said receiver-relay in the aforesaid control of said circuit-interrupter means.

'7. Ground-fault-protective relaying equipment for a polyphase transmission-line, including a signal-current pilot-channel between the ends of a line-section to be protected, and vfurther including, at each of said ends, a normally nontransmitting signal-current transmitter` and a signal-current receiver-relay associated with said pilot-channel, a line-sectionalizing circuit-interrupter means, means for providing a grounded-neutral connection to said transmission-line.

for causing the transmitter to transmit signalcurrent into said pilot-channel, means responsive to a receipt of signal-current for restraining said receiver-relay against responding, means responsive jointly to a response of said doubleduty fault-detector relaying-means and to a predetermined condition of said directional relayingmeans for causing a response of said receiver-relay in the absence of said restraint and for preventing said transmitter from transmitting signal-current into said pilot-channel, and means triply responsive to a response of said doubleduty fault-responsive relaying-means, a predetermined condition of said directional relayingmeans, and a response of said receiver-relay, for eecting a 'line-sectionalizing operation of said circuit-interrupter means.

8'.YGround-fault-protective relaying equipment for a polyphase transmission-line, including a signal-current pilot-channel between the ends of a line-section to be protected, and further including, at each of said ends, a normally non-transmitting signal-current transmitter and a signal-current receiver-relay associated with said pilot-channel, a line-sectionalizing circuitinterrupter means, means for providing a grounded-neutral connection to said transmission-line, a double-duty fault-detector relaying-means comprising an actuating member having a magnetizable circuit and magnetizing means for said magnetizable circuit, means for energizing said magnetizing means so as to be relatively strongly responsive to zero-phase-sequence line-current components and relatively weakly responsive to ground-currents in said grounded-neutral connection, the two responses being cumulative when the zero-phase-sequence line-current component is flowing out of the protected line-section, means for utilizing a response of said double-duty fault-detector relaying-means for causing the transmitter to transmit signal-current into said pilot-channel, means for utilizing a response of said double-duty fault-detector relaying-means in the control of said circuit-interrupter means and in the control of said receiver-relay, linecondition-responsive directional means, means for utilizing said directional means in the blocking of signal-current transmission, means for utilizing the receipt of signal-current in the control of said receiver-relay, and means for utilizing a response of said receiver-relay in the aforesaid control ,of said circuit-interrupter means.

9. Protective relaying equipment for a transmission-line, including a signal-current pilotchannel between the ends of a line-section to be protected, and further including, at each of said ends, a normally non-transmitting signal-curtra.

rent transmitter and a signal-current receiver-relay associated with said pilot-channel, a line-sectionalizing circuit-interrupter means, a doubleduty fault-detector relaying-means comprising an actuating member having a magnetizable circuit and magnetizing means for energizing said magnetizable circuit so as to be responsive to the vectorial resultant of a relatively large component which is relatively strongly responsive to a line-current function, and a relatively small component which is relatively weakly responsive to an electrical line-quantity which exists concurrently with said line-current function and which is of a uniform polarity regardless of the direction of the line-current, the two responses being cumulative when the line-current is owing out of the protected line-section, a directional relaying-means responsive to line-fault conditions, means for utilizing a response of said double-duty fault-detector relaying-means for causing the transmitter to transmit signal-current into said pilot-channel, means responsive to a receipt of signal-current for restraining said receiver-relay against responding, means responsive jointly to a response of said double-duty fault-detector relaying-means and to a predetermined condition of said directional relaying-means for causing a response of said receiver-relay in the absence of said restraint and for preventing said transmitter from transmitting signal-current into said pilotchannel, and means triply responsive to a response of said double-duty fault-responsive relaying-means, a predetermined condition of said directional relaying-means, and a response of said receiver-relay, for effecting a line-sectionalizing operation of said circuit-interrupter means.

10. Protective relaying equipment for a transmission-line, including a signal-current pilotchannel between the ends of a line-section to be protected, and further including, at each of said ends, a normally non-transmitting signal-current transmitter and a signal-current receiverrelay associated with said pilot-channel, a linesectionalizing circuit-interruptor means, a double-duty fault-detector relaying-means comprising an actuating member having a magnetizable circuit and magnetizing means for energizing said magnetizable circuit so as to be responsive to the vectorial resultant of a relatively large component which is relatively strongly responsive to a line-current function, and a relatively small component which is relatively weakly responsive to an electrical line-quantity which exists concurrently with said line-current function and which is of a uniform polarity regardless of the direction of the line-current, the two responses being cumulative when the line-current is flowing out of the protected line-section, means for utilizing a response of said double-duty fault-detector relaying-means forI causing the transmitter to transmit signal-current into said pilot-channel, means for utilizing a response of said doubleduty fault-detector relaying-means in the control of said circuit-interrupter means and in the control of said receiver-relay, line-condition-responsive directional means, means for utilizing said directional means in the blocking of signalcurrent transmission, means for utilizing the receipt of signal-current in the control of said receiver-relay, and means for utilizing a response of said receiver relay in the aforesaid control of said circuit-interrupter means.

11. Ground-fault-protective relaying equipment for a polyphase transmission-line, includlng a signal-current pilot-channel between the ends of a line-section to be protected, and further including, at each of said ends, a normally non-transmitting signal-current transmitter and a signal-current receiver-relay associated with said pilot-channel, a line-sectionalizing circuitinterrupter means, a double-duty fault-detector relaying-means comprising an actuating member having a magnetizable circuit and magnetizing means for energizing said magnetizable circuit so as to be responsive to the vectorial resultant of a relatively large component which is relatively strongly responsive to zero-phase-sequence linecurrent components, and a relatively small component which is relatively weakly responsive to a zero-phase-sequence line-quantity which exists concurrently with said zero-phase-sequence linecurrent components and which is of a uniform vpolarity regardless of the direction of the zerophase-sequence line-current component, the two responses being cumulative when the zero-phasesequence line-current component is flowing out of the protected line-section, a directional relaying-means responsive to fault conditions, means` for utilizing a response of said double-duty faultdetector relaying-means for causing the transmitter to transmit signal-current into said pilotchannel, means responsive to a receipt of signalcurrent for restraining said receiver-relay against responding, means responsive jointly to a response of said double-duty fault-detector relaying-means and to a predetermined condition of said directional relaying-means for causing a response of said receiver-relay in the absence of said restraint and for preventing said transmitter from transmitting signal-current into said pilot-channel,

and means triply responsive to a response of said double-duty fault-responsive relaying-means, a predetermined condition ofsaid directional relaying-means, and a response of said receiverrelay, for effecting a line-sectionalizing operation of said circuit-interrupter means.

12. Ground-fault-protective relaying equipment for a polyphase transmission-line, including a signal-current pilot-channel between the ends of a line-section to be protected, and further including, at each of said ends, 'a normally nontransmitting signal-current transmitter and a signal-current receiver-relay associated with said pilot-channel, a line-sectionalizing circuit-interrupter means, a double-duty fault-detector relaying-means comprising an actuating member having amagnetizable circuit and magnetizing means for energizing said magnetizable circuit so as to be responsive to the vectorial resultant of a relatively large component which is relatively stronglyesponsive to zero-phase-sequence linecurrent components, and a relatively small component which is relatively weakly responsive to a zero-phase-sequence line-quantity which exists concurrently with said zero-phase-sequence linecurrent components and which is of a uniform polarity regardless of the direction of the zerophase-sequence line-current component, the two responses being cumulative when the zero-phasesequence line-current component is owing out of the protected line-section, means for 'utilizing a response of said double-duty fault-detector relaying-means for causing the transmitter to transmit signal-current into said pilot-channel, means for utilizing a response of said doubleduty fault-detector relaying-means in the control of said circuit-interrupter means and in the control of said receiver-relay, line-condition-responsive directional means, means for utilizing said directional means in the blocking of a signalcurrent transmission, means for utilizing thereceipt of signal-current in the control of said receiver-relay, and means for utilizing a response of said receiver-relay in the aforesaid control of said circuit-interrupter means.

13. Ground-fault-protective relaying equipment for a polyphase transmission-line, including a signal-current pilot-channel between the ends of a line-section to be protected, and iurther including, at each of said ends, a normally non-transmitting.signal-current transmitter and a signal-current receiver-relay associatedA with said pilot-channel, a line-sectionalizing circuitinterrupter means, means for providing a grounded-neutral connection to said transmission-line, a double-duty fault-detector relayingmeans comprising an actuating member having a magnetizable circuit and magnetizing means for energizing said magnetizable circuit so as to be responsive to the vectorial resultant of a relatively large component which is relatively strongly responsive to zero-phase-sequence line-current components, and a relatively small component which is relatively weakly responsive to zerophase-sequence line-voltage components, the two responses being cumulative when the zero-phasesequence line-current component is owing out of the protected line-section, a directional relaying-means responsive to ground-fault condition, means for utilizing a response of said double-duty fault-detector relaying-means for causing the transmitter to transmit signal-current into said pilot-channel, means responsive to a receipt of signal-current for restraining said receiver-relay against responding, means responsive jointly` to a response of said double-duty fault-detector relaying-means and to a predetermined condition of said directional relaying-means for causing a response of said receiver-relay in the absence of said restraint and for preventing said transmitter from transmitting signal-current into said pilotchannel, and means triply responsive to a response of said double-duty fault-responsive relaying-means, a predetermined condition of said directional relaying-means, and a response of said receiver-relay, for eiecting a line-sectionalizing operation of said circuit-interruptor means.

14. Ground-fault-protective relaying equipment for a polyphase transmission-line, including a signal-current pilot-channel between the ends of a line-section to be protected, andtfurther including, at each of said ends, a normally non-transmitting signal-current transmitter and a signal-current receiver-relay associated with said pilot-channel, a line-sectionalizing circuitinterrpter means, means for providing a grounded-neutral connection to said transmission-line, a double-duty fault-detector relaying-means comprising an actuating member having a magnetizable circuit and magnetizing means for energizing said magnetizable circuit so as to be responsive to the vectorial resultant of a relatively large component which is relatively strongly responsive to zero-phase-sequence line-current components, and a relatively small component which is relatively weakly responsive to zerophase-sequence line-voltage components, the two responses being cumulative when the zero-phasesequence line-current component is flowing out of the protected line-section, means for utilizing a response of said double-duty fault-detector relaying means forv causing the transmitter to transmit signal-current into said pilot-channel, means for utilizing a response of said doubleduty fault-detector relaying-means in the control of said circuit-interrupter means and ln the control of said receiver-relay, line-condition-responrelay, and means for utilizing a response of said receiver-relay in the aforesaid control -of said circuit-interrupter means.

15. Ground-fault-protective relaying equipment for a polyphase transmission-line, including a signal-current pilot-channel between the ends of a line-section to be protected, and further including, at each of said ends, a normally nontransmitting signal-current transmitter and a signal-current receiver-relay associated with said pilot-channel,v a line-sectionalizing circuit-interrupter means, means for providing a groundedneutral connection to said transmission-line, a double-duty fault-detector relaying-means comprising an actuating member having a magnetizable circuit and magnetizing means for energizing said magnetizable circuit so as to be responsive to the vectorial resultant of a relatively large component which is relatively strongly responsive to zero-phase-sequence line-current components, and a relatively small component which is relatively weakly responsive to ground-currents in said grounded-neutral connection, the two responses being cumulative when the zero-phasesequence line-current component is owing out of the protected line-section, a directional relaying-means responsive to ground-fault conditions, means for utilizing a response of said double-duty fault-detector relaying-means for causing the transnitter to transmit signal-current into said pilot-channel, means responsive to a receipt of signal-current for restraining said receiver-relay against responding, means responsive jointly to a response of said double-duty fault-detector relaying-meansand to a predetermined condition of said directional relaying means, for causing a response of said receiver-relay in the absence of said restraint and for preventing said transmitter from transmitting signal-current into said pilot-channel, and means triply responsive to a response of said double-duty fault-responsive relaying-means, a predetermined condition of said directional` relaying-means, and a response of said receiver-relay, for eiecting a line-sectionalizing operation of said circuit-interrupter means.

16. Ground-fault-protective relaying equipment for a polyphase transmission-line, including a signal-current pilot-channel between the ends of a line-section to be protected, and further including, at each of said ends, a normally nontransmitting signal-current transmitter and a signal-current receiver-relay associated with said pilot-channel, a line-sectionalizing circuit-interrupter means, means for providing a groundedneutral connection to said transmission-line, a double-duty fault-detector relaying-means comprising an actuating member having a magnetizable circuit and magnetizing means for energizing said magnetizable circuit so as to be respon- Y sive to the vectorial resultant of a relatively large component which is relatively strongly responsive to zero-phase-sequence line-current components, and a relatively small component which is relatively weakly responsive to ground-currents in said grounded-neutral connection, the two responses being cumulative when the zero-phasesequence line current component is owing out of the protected line-section, means for utilizing a response of said double-duty fault-detector rerectional means in the blocking of signal-current transmission, means for utilizing the receipt of signal-current in the control of said receiverrelay, and means for utilizing a response of said receiver-relay in the aforesaid control of said 5 circuit-interrupter means.

BERNARD E. LENEHAN. 

